If you were an audio purist, you would use caps like those listed on page 14 of this catalog.http://www.thetubecenter.com/files/TheTubeCenter_-_Vacuum_Tube_Catalog.pdf

However, you could use plain old ceramic capacitors for C5 & C6, and aluminum electrolytics for C10 & C2 and never notice the difference if amplifying the 8-bit PWM signal from an ATMega328 for example.You could apply some math to the values too, see what kind of filtering is being applied. The 100uF on the output could end up limiting the bass response, so a 220uF, maybe even 470uF, could be better there.

Capacitors have more parameters associated with them than just their rated capacitance and max voltage rating. In particular, all capacitors also have what are called equivalent series resistance (ESR), equivalent series Inductance (ESL), and leakage resistance. And the different types of capacitors all have different ranges of these parameters. They all also have different responses to temperature variations, some are very stable across wide ranges of temperatures and others have various variations that are temperature dependent.

Decoupling (across the supply) Ceramic for values 0.1uF and lower and electrolytic (aluminum) for values above. You could use tantalum here but they are expensive and a fire hazard.Audio coupling - polyester, polystyreneHigh stability / high frequency - Silver Mica (these are only available in small values anyway and have a negative temperature coefficient)

Being a complete noob.. and trying to learn to read/understand schematics a bit better..

but how do you know what TYPE of capacitor to use?

Even professional engineers with years of experience don't always know what type of capacitor to choose, so don't feel bad. There are rules of thumbs out in the industry that engineers follow which aren't true or aren't true anymore. When it comes down to it, there are a lot of "it depends" conditions for choosing the right cap.

I've been meaning to write an article on "Capacitors for Hobbyist."

BTW, most hobby style projects can get away with just ceramics. If audio is a concern, use C0G / NPO type ceramics.

some of that helped alot. (I wasnt looking for what to use on the schematic.. but how to learn to tell for myself, in general)

to summarize.. to see if I 'got it'

1.) (It depends!) LOL2.) big(er) values will command/default it to be a electrolytic type3.) 'De-coupling' caps for small values up to around 0.1uF will be 'ceramic'4.) 'De-coupling' caps for larger values will be electrolytic (aluminum)

*** (again sorry for noob question..how do I tell a de-coupling cap vs another (Audio coupling?)? just by the placement? and overtime/experience of what the cap's purpose is?)

5.) 'Audio coupling' caps are usually polyester/polystyrene type6.) High Stability/Freq -Silver Mica type (never even heard of these I dont think... I have mostly been limited to whats available at RadioShack =( (dont laugh!)

but I dont have one of those.. (I have an electrolytic one though? would it work.)

Is there any 'rule' or 'tip' on what can be substituted for what? (again only type) or as long as the 'values' match.. its interchangeable? (which I dont think it the case...is it?)

Again thanks guys..it helps a bit

(I have a new thread coming soon. asking for help on what 'exact' components to order.. ordering form Digikey/Mouser..etc is a bit 'overwhelming to the noob out there.. (lots of choices for each part..etc)

Looking to order a few 'shift register' chips I guess..

and probably some grabs bags of caps of all values & types off ebay?? (or another suggestion?)

5.) 'Audio coupling' caps are usually polyester/polystyrene type6.) High Stability/Freq -Silver Mica type (never even heard of these I dont think... I have mostly been limited to whats available at RadioShack =( (dont laugh!) 7.) If AUDIO is a concern/focus, use: C0G / NPO type ceramics capacitors

#5 and #6 are the same. If a ceramic C0G/NPO doesn't have enough capacitance (they are low capacitance but high stability) then Film capacitors (polyester / polystyrene) might be necessary. I'd also say that C0G ceramics are a replacement for #6.

C0G/NP0 ceramics can be used in audio circuits. (This is one of those rules of thumb I mentioned. Many say "No Ceramics in audio!!" You just have to avoid ceramics made with barium titanite: Z5U, Y5V, X5R, X7R, etc.)

Tantalum is a solid electrolytic. In this case, if the output of the amplifier can get to 9V then a 10V tantalum is absolutely not acceptable. Standard Tantalums need to be de-rated by 50% for reliability. So a >18V (25V) should have been specified.

I would recommend the same de-rating for Aluminum (wet) Electrolytic caps as well.

Tantalum might have been suggested since they are looking for a high capacitance (100µF) and wanted low ESR. Ceramic isn't an option because you'd need to use X5R (which is bad for audio.) Tantalum generally has lower ESRs than Aluminum (and the very least have ESR stability over temperature.)

For basic projects, I usually just consider whether or not the capacitor must be polarized or not. If the capacitor must be non-polar, I'll go with a ceramic. If the schematic calls for a polar capacitor, I'll use an electrolytic. Note that there are also non-polar electrolytics, and most non-polar caps will work where polar ones are designated.

and on any schematic.. it wil be 100% for sure labeled as such if it needs to be polarized?

Using the qualifiers "any" and "100%" the answer is easily: No. The difference only exists because the nature of the capacitor type's construction (not because of inherent advantages). So it depends on if the capacitor being used can tolerance whatever voltages will be applied to it. E.g., if used in an amplifier where the voltage may go negative (reverse) then you probably cannot use a polarized cap. You might see a note about not using a polarized device, but don't rely on that being stated.

Yup, we (I work for KEMET) and there rest of the industry use anode (+) and cathode (-).

I know about the marking of positive and/or negative terminals, but again I've never seen a reference to calling them the anode and cathode terminals, as that is normally restricted to semiconductors and vacuum tubes. So can you show us any capacitor datasheet using the the words cathode and anode for the terminals?

I'm really not trying to be argumentative, just having been in electronics for 50+ years I can't ever recall ever reading or hearing the cap terminals using those terms.

Batteries have positive and negative terminals, but I've also never heard of them referred to as the anode and cathode terminals.

Yup, we (I work for KEMET) and there rest of the industry use anode (+) and cathode (-).

I know about the marking of positive and/or negative terminals, but again I've never seen a reference to calling them the anode and cathode terminals, as that is normally restricted to semiconductors and vacuum tubes. So can you show us any capacitor datasheet using the the words cathode and anode for the terminals?

Yup, we (I work for KEMET) and there rest of the industry use anode (+) and cathode (-).

I know about the marking of positive and/or negative terminals, but again I've never seen a reference to calling them the anode and cathode terminals, as that is normally restricted to semiconductors and vacuum tubes. So can you show us any capacitor datasheet using the the words cathode and anode for the terminals?

From that link you posted, calling it the positive terminal rather then the 'anode' terminal, that is my issue. Again I would bring up the common battery terminal name usage.

Quote

Reverse VoltageSolid tantalum capacitors are polar devices and may be permanently damaged or destroyed if connected with the wrong polarity. Thepositive terminal is identified on the capacitor body by a stripe plus in some cases a beveled edge. A small degree of transient reversevoltage is permissible for short periods per the table. The capacitors should not be operated continuously in reverse mode, even withinthese limits.